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Reduced abiraterone acetate dose with low-fat meal maintains efficacy, saves costs
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Taking a quarter dose of abiraterone acetate with a low-fat breakfast appeared noninferior to taking a standard dose in a fasting state among men with castration-resistant prostate cancer, according to results of a randomized phase 2 clinical trial presented at the Genitourinary Cancers Symposium.
This dose reduction could result in a savings of thousands of dollars per month.
“We know this drug is absorbed much more efficiently when taken with food,” Russell Szmulewitz, MD, assistant professor of medicine at The University of Chicago, said in a press release. “It’s inefficient — even wasteful — to take this medication while fasting, which is how the drug’s label says to take it.”
Abiraterone acetate (Zytiga, Janssen) — approved by the FDA in 2011 for use in combination with prednisone — has become a standard of care for treatment of metastatic castration-resistant prostate cancer. The drug’s label recommends 1,000 mg daily in combination with 5 mg prednisone and advises taking the drug on an empty stomach, with patients fasting at least 2 hours before and 1 hour after administering.
Abiraterone acetate costs more than $8,000 per month, with health insurance copays often ranging from $1,000 to $3,000 per month. Because patients with castration-resistant prostate cancer typically remain on this therapy for 12 to 18 months, researchers hypothesized that if the patients could achieve the same results with reduced daily dosage, they could save up to $6,500 a month.
In their multicenter study, Szmulewitz and colleagues analyzed 72 patients (median age, 74 years) from seven institutions in the United States and Singapore whose disease had progressed despite standard initial hormonal therapy. Baseline PSA was 39.2 (range, 0.6-1,789).
Thirty-six men were assigned the standard dose of 1,000 mg of abiraterone acetate once a day on an empty stomach, and 36 received 250 mg once a day with a low-fat breakfast. Both arms received 5 mg of prednisone twice daily.
Researchers assessed PSA monthly and testosterone levels every 12 weeks along with standard disease burden. Patients provided pharmacokinetic samples at day 1 and 8, and at months 2, 3 and 4.
Changes in PSA response rate from baseline to week 12 served as the primary endpoint. The study’s design was based on a noninferiority margin of 15% (standard deviation, 0.51).
Despite a 75% reduction in dose, researchers found no statistically significant difference in abiraterone acetate activity as measured by variation in PSA levels between the two arms (mean log change, –1.59 vs. -1.19; 95% CI, –0.4 to 1.19). The noninferiority of the low-dose arm was established with a standard deviation of –0.24.
The median time to disease progression was also nearly identical, at approximately 14 months in both arms.
Patients who took abiraterone acetate with food also were less likely to report stomach discomfort.
“Given the pharmacoeconomic implications, our results warrant consideration by doctors who care for prostate cancer patients as well as payors,” Szmulewitz said, adding that abiraterone acetate is a “great medication that has shifted the standard of care.”
Researchers noted the small number of participants in their study as a limitation and warned that patients with prostate cancer should not begin experimenting with their medication.
“This was a relatively small study, too small to show with confidence that the lower dose is as effective,” Szmulewitz said. “It gives us preliminary, but far from definitive, evidence. Physicians should use their discretion, based on patient needs.” – by Chuck Gormley
Reference:
Szmulewitz RZ, et al. Abstract 176. Presented at: Genitourinary Cancers Symposium; Feb. 16-18, 2017; Orlando, Fla.
Disclosure: HemOnc Today could not confirm the researchers’ relevant financial disclosures at the time of reporting.